ASVAB Mechanical Comprehension Practice Test 42790 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.95
Score	0%	59%

Review

1 If the radius of the axle is 3 and the radius of the wheel is 4, what is the mechanical advantage of this wheel and axle configuration?

53% Answer Correctly

	1.33
	3
	0.75
	1

Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 4 and the output radius (where the resistance is being applied) is 3 for a mechanical advantage of \( \frac{4}{3} \) = 1.33

2 What is the power output of a 3 hp engine that's 95% efficient?

40% Answer Correctly

	31 \( \frac{ft⋅lb}{s} \)
	3135 \( \frac{ft⋅lb}{s} \)
	522.5 \( \frac{ft⋅lb}{s} \)
	1567.5 \( \frac{ft⋅lb}{s} \)

Solution

\( Efficiency = \frac{Power_{out}}{Power_{in}} \times 100 \)
Solving for power out: \( P_{o} = \frac{E \times P_{i}}{100} \)
Knowing that 1 hp = 550 \( \frac{ft⋅lb}{s} \), P_i becomes 3 hp x 550 \( \frac{ft⋅lb}{s} \) = 1650 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{95 \times 1650 \frac{ft⋅lb}{s}}{100} \) \( = \frac{156750 \frac{ft⋅lb}{s}}{100} \) = 1567.5 \( \frac{ft⋅lb}{s} \)

The standard unit of energy is the:

73% Answer Correctly

	Volt
	Joule
	Watt
	Horsepower

Solution

The Joule (J) is the standard unit of energy and has the unit \({kg \times m^2} \over s^2\).

Which of these will have the most impact on the kinetic energy of an object?

54% Answer Correctly

	its speed
	its mass
	its direction
	its weight

Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.

What type of load acts on a relatively small area of a structure?

75% Answer Correctly

	impact load
	concentrated load
	dynamic load
	non-uniformly distributed load

Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.